This invention relates to a multi-fuel, precombustor unit that provides a combustion system for any type of fuel, liquid or gas, or a combination of both liquid and gas. The combustor unit can be used in any type of engine, spark ignited or compression ignited. The combustor unit is particularly useful in adapting a diesel engine to natural gas or methanol. In such units direct conversion, where gas is supplied to the air intake, performance is compromised. The low pressure natural gas displaces a volume of air, and on compression of the mixture, a substantial reduction in power may result. Furthermore, the compression ratio must be reduced from the operating level of diesel fuel to match the acceptable octane number of a gas-air mixture. The combustion of the gas-air mixture is usually very explosive with an unusually high heat release that generates oxides of nitrogen. Attempts to inject the gas into the cylinder during the later part of the compression require high pressure gas compressors that provide a substantial drain on the net work output of the engine. Similar problems arise from converting gasoline engines to natural gas or exotic gas and liquid fuel combinations.
The precombustor unit of this invention has application further as an auxiliary component for installation into diesel engines for trucks and buses that are used in urban environments. Diesel engines are extremely inefficient at low speeds of operation and generate noxious emissions, particularly hydrocarbon particulate matter. Often diesel engines in buses and trucks must remain in operation while the vehicle is stopped for long periods of time to maintain on-board, electrical power generation equipment for lighting or refrigeration. At such idle speeds, the engine is operating at its worst efficiency, generating noxious fumes in the area of the idled vehicle. Switching to the use of an auxiliary fuel supply to power the engine at low end speeds is both fuel effective and useful to substantially abate pollution. Particularly when a natural gas fuel is used, the levels of pollution drop dramatically.